What are muscle cramps?

A muscle cramp is an involuntarily and forcibly contracted muscle that does not relax. When we use the muscles that can be controlled voluntarily, such as those of our arms and legs, they alternately contract and relax as we move our limbs. Muscles that support our head, neck, and trunk contract similarly in a synchronized fashion to maintain our posture. A muscle (or even a few fibers of a muscle) that involuntarily (without consciously willing it) contracts is in a "spasm." If the spasm is forceful and sustained, it becomes a cramp. Muscle cramps often cause a visible or palpable hardening of the involved muscle.

Muscle cramps can last anywhere from a few seconds to a quarter of an hour or occasionally longer. It is not uncommon for a cramp to recur multiple times until it finally resolves. The cramp may involve a part of a muscle, the entire muscle, or several muscles that usually act together, such as those that flex adjacent fingers. Some cramps involve the simultaneous contraction of muscles that ordinarily move body parts in opposite directions.

Muscle cramps are extremely common. Almost everyone (one estimate is about 95%) experiences a cramp at some time in their life. Muscle cramps are common in adults and become increasingly frequent with aging. However, children also experience cramps of muscles.

Any of the muscles that are under our voluntary control (skeletal muscles) can cramp. Cramps of the extremities, especially the legs and feet, and most particularly the calf (the classic "charley horse"), are very common. Involuntary muscles of the various organs (uterus, blood vessel wall, bowels, bile and urine passages, bronchial tree, etc.) are also subject to cramps. Cramps of the involuntary muscles will not be further considered in this review. This article focuses on cramps of skeletal muscle. Continue Reading

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.